The objectives of this proposal are to study the control of phospholipid synthesis during the development of the liver and lung. Previous experiments with liver and lung slices have shown that the pathway for the synthesis of choline phosphoglyceroles, ethanolamine phosphoglycerides, inositol phosphoglycerides, and serine phosphoglycerides increase during development. The present project will involve the detailed study of the activities and properties of the individual enzymes in each pathway. The following enzyme reactions will be investigated: choline phosphokinase, ethanolamine phosphokinase, acyl-CoA-GPC acyl transferase, CTP:choline phosphate cytidyl transferase, CTP:ethanolamine phosphate cytidyl transferase, CDP- choline:1,2-diglyceride transferase, CDP-ethanolamine: 1,2-diglyceride transferase, phosphatidic acid phosphohydrolase, the formation of CDP- diglyceride, the formation of inositol phosphoglyceride from CDP- diglyceride and myo-inositol, the Ca ion-exchange reaction of L-serine with phosphatidyl-ethanolamine, and the decarboxylation of phosphatidylserine. In addition, the concentration of CTP and the activities of the enzymes, nucleotide kinase and nucleoside diphosphokinase will be studied during liver and lung development.